1. Field of the Invention
The present invention relates to a cleaning method and apparatus for a curved glass sheet used in an adhesion process for adhering laminated glass (safety glass) such as a windshield of a vehicle.
2. Description of the Prior Art
In a conventional windshield of a vehicle, a plurality of sheets of plate glass are adhered together through a plastic film such as a polyvinyl butyral film to prepare so-called safety glass. Such laminated glass is prepared such that the overlapped sheets of plate glass are heated to be formed into a desired shape, and that an adhesion interlayer is inserted between the separated curved sheets of plate glass and the resultant structure is subjected to adhesion. In order to easily separate the curved sheets of plate glass, diatomaceous earth particles or the like are sprinkled between the sheets of plate glass. Before the adhesion interlayer is inserted between the curved glass sheets, cleaning must be performed to remove all the diatomaceous earth particles from the surfaces of the curved glass sheets which are to be subjected to adhesion. In principle, according to dry cleaning, a roll brush is rotated and is brought into slidable contact with the curved glass surface so as to clean it. A conventional cleaning apparatus of this type basically comprises a drive mechanism of the roll brush, a moving mechanism for feeding the roll brush along the curved glass surface, and a vacuum suction mechanism for removing diatomaceous earth particles from the glass surface. The moving mechanism has a guide cam mechanism for moving the brush along the curved surface of the glass sheet. Whenever the shape of the glass sheet changes corresponding to a windshield of a different type of vehicle, the guide cam must be replaced with the one that is compatible with the new glass sheet shape. Thus, this cleaning apparatus is not suitable for cleaning different types of curved glass sheets. In addition, vehicle windshields have a complicated three-dimensional surface wherein the radius of curvature at the upper side differs from that at the lower side. As a result, the entire area of the front glass cannot be uniformly brushed in accordance with the roll brush movement controlled by the guide cam. In addition to this disadvantage, it is essentially difficult to control a flexible roll brush in accordance with a rigid guide cam. The guide cam cannot provide highly precise and uniform brushing, thus degrading the cleaning precision. The roll brush is brought into nonuniform contact with the glass surface, so the brush life is shortened and the brushing state is deteriorated, resulting in inconvenience over time. When the brush is reciprocated along the glass surface, the locus of the brush along the forward direction differs from that along the reverse direction due to mechanical play of the roll brush moving mechanism and undershooting or overshooting of the servo mechanism. Therefore, at present, even if the prescribed brushing operation can be performed along the active direction, the same result as in the active direction may not be obtained along the inactive direction.